The invention relates to a diaphragm which can be implanted in the lens capsule sac of an eye to create an artificial pupil aperture.
The state of the art in medicine is to treat gray star (cataracts) by surgical removal of the cloudy lens and to insert an artificial intraocular lens in the lens capsule sac of the eye.
To take care of iris deficiencies, there are known aniridia intraocular lenses, which are transparent within the meaning of diopter optics only in the zone of a central artificial pupil aperture and are colored at the periphery.
The use of an aniridia intraocular lens is not necessarily considered when minor defects of the iris exist. A disadvantage of this fixed combination of diaphragm with diopter optics is the generally poor or not direct availability of this prosthesis. This is due on the one hand to the complex manufacture and on the other hand to storage-related reasons, since it would be too expensive and economically unfeasible to keep a stock of all diopter strengths for non-routine cases.
Especially when complications exist, it is known that a bracing ring can be inserted as a further prosthesis in the lens capsule sac in addition to the intraocular lens, in order to brace and stabilize it and to relieve the load on the suspensory apparatus of the lens capsule. This takes place by pressure of the capsule bracing ring on the equatorial region of the capsule sac.
In the case of aniridia or of iris coloboma, the prosthetic possibility also exists of a capsule bracing ring with, for implantation in the capsule sac, one or more inwardly projecting diaphragms which are intended to leave open a central artificial pupillary aperture.
The combination of capsule bracing ring and diaphragm misses its objective, or in other words that of creating an artificial pupil of specified size, in that the "principle of action" is opposed thereto. Whereas the bracing ring exerts its bracing effect on the equatorial region of the capsule sac, the target direction of the diaphragms fixed thereto lies in the direction of the center of the capsule sac. This is the case in order to obtain an artificial pupil aperture of specified size. Because of the bracing effect, the diaphragms can become displaced behind the sclera boundaries (limbus), thus producing a too large artificial pupil aperture. As far as the pupil aperture is concerned, the result of this implant is greatly dependent on the anatomical conditions of the capsule sac and is not predictable. Thus this prosthesis does not fulfill the objective of creating a pupil aperture of specified size.
The object of the invention is to create, for implanting in the lens capsule sac of an eye, a diaphragm that is functionally decoupled from a capsule bracing ring and creates a pupil aperture of specified size.
This object is achieved with a diaphragm which, together with an artificial lens, can be implanted substantially without stress in the lens capsule sac of an eye.
The concept of this diaphragm is based on the fact that the capsule sac equator primarily exerts no force on the (compressible) diaphragm. This has the advantage that the pupil sizes defined by design remain unchanged. Further advantages of the presented concept are the uncomplicated implantability and the direct availability because of the independence from an optical system.
In a preferred embodiment, the diaphragm fits without stress in a circle of 10.5 mm to 11 mm diameter, or of up to 12 mm diameter and larger when used for very large eyes. The diaphragm extends to the circle on opposite sides.
The diaphragm can be a single diaphragm with an overlap region on one side next to a central open space and a stirrup-shaped haptic member on the other side thereof.
The haptic member is preferably C-shaped or J-shaped.
The diaphragm can also be a double diaphragm with two overlap regions on both sides of a central open space and one elastic stirrup therebeside, joining the overlap regions.
The stirrup is preferably curved inwardly in the form of a U.
The diaphragm according to the invention is preferably flat on the whole. However, it can also have one or more flat overlap regions and a haptic member angled away therefrom.
In a preferred embodiment, there can be inserted in the diaphragm a stitch which stiffens the diaphragm in the lens capsule sac after completion of implantation.
The diaphragm can be provided with one or more openings for a needle tip or a guide hook.
The diaphragm preferably comprises colored PMMA (polymethyl methacrylate) or polycarbonate.
By virtue of the invention there is created a kit of diaphragms which can be implanted one above the other with angular offset in the capsule sac, thus overlapping each other such that a central, approximately circular pupil aperture is left open.
The invention provides one kit of diaphragms each for artificial pupil apertures of 3 mm and 4 mm diameter.
In a preferred embodiment, the diaphragms of the kit can be joined with each other in the intracapsular region, and in particular can be clamped, clipped or snapped together with each other.
In a preferred embodiment, there is provided a fixing ring with a circular aperture for latching in one or more diaphragms of the said type. An exactly circular artificial pupil aperture is created by the fixing ring.
According to a further variant of the invention there is provided a circular diaphragm which comprises a foldable colored material, especially silicone or soft acrylic. For stress-free implantation in the lens capsule sac, the outside diameter of this diaphragm is 10.5 to 11 mm, or up to 12 mm and larger if used for very large eyes. The inside diameter of the diaphragm corresponds to that of the desired artificial pupil aperture, especially 3 mm or 4 mm.